Hydraulic rotary dampener

ABSTRACT

A rotary dampener includes a cylinder with a piston threaded in the cylinder such that relative rotary motion between the cylinder and piston causes axial movement of the piston in the cylinder. Hydraulic fluid in the cylinder is forced through a bypass passage in the cylinder from one side of the piston to the other in response to the axial movement of the piston. By restricting the passage, a proper degree of dampening of relative rotary motion between the piston and cylinder and thus between first and second members secured to these components can be realized.

I United States Patent [151 3,653,46 1

Huxley, III et al. 5] Apr. 4, 1972 [541 HYDRAULIC ROTARY DAMPENER 2,404,611 7/1946 Ashbaugh ..92/8 [72] Inventors: Thomas C. Huxley, In Camarmo; gglalrd Franklin w. noose Monrovia, both of Cahf' Primary Examiner-Reinaldo P. Machado [73] Assignee: Del Mar Engineering Laboratories, Los y my h, ROSKOIIBL Pavitl Angeles, Calif. [57] ABSTRACT [22] Filed: July 23, 1970 A rotary dampener includes a cylinder with a piston threaded [2H APPI' 57562 in the cylinder such that relative rotary motion between the cylinder and piston causes axial movement of the piston in the 52 us. Cl ..1s2/2, 92/9 cylinder' Ydmulic fluid the cylinder is forced through a [51] Inn CL W866- 11/04, F] 5b 15/22 pass passage in the cylinder from one side of the piston to the 58 Field of Search ..1s2/2,222;92/9, s', 11 eslwnse the axial mmemem Pismn- BY restricting the passage, a proper degree of dampening of rela- [56] References Cited tive rotary motion between the piston and cylinder and thus I l,l26,900 2/l9l5 between first and second members secured to these components can be realized.

10 Claims, 4 Drawing Figures Patented April 4, 1972 Fl G. 2

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THOMAS C. HUXLEY III FRANKLIN W. DOOSE azdfazya/a 6% FIG. 3

A TTORNEYS HYDRAULIC ROTARY DAMPENER This invention relates generally to dampening devices and more particularly to a novel hydraulic rotary dampener for dampening swinging movements between first and second members.

BACKGROUND OF THE INVENTION There are many instances in which it isdesirable to dampen a rotary type or swinging motion. One such important instance is in thecase of a basket or frame supported on the end of a boom wherein the basket supports a man in a desired position to carry out certain operations. Because the boom structure itself normally starts from a horizontal position towards a vertical position, the basket or frame structure carrying the man must be pivotally mounted to the end of the boom so that it will by gravity continuously assume an upright position throughout movement of the boom. On the other hand, the pivotal mounting for the basket can result in swinging type oscillations of the basket. It is therefore desirable to dampen such swinging movements and preferably such dampening should be critical in nature so that the basket will not oscillate but stay in substantially its proper upright orientation even for relatively rapid movements of the boom structure.

l-Ieretofore, dampening of the swinging movement of the basket has been accomplished by the use of a shock absorber secured to the basket and a strut member supporting the basket...The shock absorber bridges the pivot point so that swinging movement of the basket will be inhibited by the shock absorber.

, Another alternative is to use a double ended hydraulic cylinder and piston bridging the pivot so that swinging movement causes the cylinder piston to move in and out of the cylinder. While dampening can be achieved with this system, the degree of the dampening is not constant because of the geometry of the mounting. Further, excessive length is created by the double shaft end which is necessary to balance equal hydraulic volumes on either side of the piston. Any side thrust on the basket can cause serious damage to the piston and the strains on the basket and strut sections because of the single shear mounting can become excessive.

BRIEF DESCRIPTION OF THE PRESENT INVENTION With the foregoing in mind, it is a purpose of the present invention to provide a novel hydraulic rotary dampener particularly suitable for dampening swinging movements of a heavy mass such as a basket on the end of a boom structure wherein problems associated with the prior art systems are avoided.

In accord with the invention, a cylinder having a central cylindrical chamber, a reduced diameter first end opening and a reduced diameter second end opening, includes internal screw threads in the second end opening. A piston body in turn is supported by a piston rod intermediate the ends of the rod, these ends being positioned in the reduced diameter end openings of the cylinder. One end portion of the piston rod is provided with the external screw threads mating with the internal screw threads in the reduced diameter end opening of the cylinder so that relative rotation of the piston rod and cylinder causes the piston body to move axially in the central cylindrical chamber. This central cylindrical chamber is filled with hydraulic fluid. A fluid passage means preferably formed in the cylinder itself places a portion of the cylindrical chamber on one side of the piston body in communication with the portion of the cylindrical chamber on the other side of the piston body so that axial movement of the piston body forces fluid to move through the fluid passage means from one side of the piston to the other. A suitable fluid passage restricting means such as a needle valve is provided so that the degree of dampening; that is, the degree of resistance to movement of the piston body can be adjusted.

With the foregoing arrangement, the dampening of swinging movement of a basket relative to a supporting strut on the end of a boom can readily be achieved by securing the piston rod to the basket and the cylinder to one of the boom struts, the axis of relative swinging being coincident with the axis of the cylinder and piston rod. Swinging movements of the basket will thus cause an axial movement of the piston body in the cylinder because of the threaded connection between the piston rod and cylinder. Because of the presence of the hydraulic fluid and restricted passageway, the resistance to such swinging movements can be adjusted from free swinging through a full range of dampening resistance to an actual locked position or a position to provide critical dampening.

The axial length of the cylinder can be made extremely short since the axial travel caused by the threaded connection is relatively short. Thus a very compact unit can be provided with the advantage of easy maintenance and installation.

BRIEF DESCRIPTION OF THE DRAWINGS A better understanding of the invention will be had by referring to the accompanying drawings, in which:

FIG. 1 is a fragmentary perspective view of a basket and boom structure incorporating a prior art type of dampening device to inhibit swinging movements of the basket;

FIG. 2 is a view similar to FIG. 1 showing the hydraulic rotary dampener of this invention substituted for the prior art dampener to inhibit swinging movements of the basket;

FIG. 3 is a greatly enlarged fragmentary view partly in cross section taken generally in the direction of the arrows 3-3 of FIG. 2; and

FIG. 4 is an exploded perspective view of a portion of the structure illustrated in FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED I EMBODIMENT Referring first to FIG. 1 there is shown a basket structure 10 for supporting a man on the end of a boom. The end portion of the boom may include struts 11 and 12 pivotally connected to opposite sides of the basket 10 for rotation about an axis A. With this arrangement, and a man standing in the basket 10, the center of gravity of the basket will be below the pivot axis A so that the basket will normally remain upright even though the angle of the supporting boom should change.

In order to dampen swinging movements of the basket, it has been customary heretofore to provide shock absorber or alternatively a double ended hydraulic cylinder such as shown at 13 connected between the strut and the basket structure itself as schematically indicated. The cylinder thus bridges the pivot point 14 such that any swinging movement as indicated by the double headed arrow 15 will cause the piston to move back and forth in the cylinder. Suitable hydraulic fluid in the cylinder will thus effectively dampen such swinging movement.

The present invention provides an improved hydraulic rotary dampening device which serves in its preferred embodiment as a substitute for the cylinder 13 to dampen movements of the basket. Thus, in FIG. 2 there is illustrated at 16 the improved hydraulic rotary dampener connected between the strut 11 and side of the basket 10. It will be noted that this unit is considerably more compact than the double acting cylinder 13 described in FIG. 1. The opposite strut 12 is journalled to the opposite side of the basket as indicated at 17.

Referring now to the detailed partial cross sectional view of FIG. 3, the hydraulic rotary dampener 16 will be described.

As shown, the rotary dampener includes a cylinder 18 having an interior cylindrical chamber 19 within which there is positioned a piston body 20. The periphery of this body is in sealing engagement with the interior cylindrical wall of the chamber 19 as by a large diameter O-ring 21.

The cylinder 18 itself includes a reduced diameter first end opening 22 and a reduced diameter second end opening 23. These openings respectively include O-rings 24 and 25 for engaging opposite ends of a piston rod 26 and are bearing surfaces for the piston rod. The piston body 20 is mounted intermediate the ends of the piston rod 26 as shown.

One end of the piston rod 26 includes an enlarged diameter mounting portion 27 which may be, for example, secured to a side of the basket 10. The other end of the piston rod 26 includes external screw threads 28. These screw threads mate with internal threads 29 formed on the interior of the reduced diameter second end portion 25 of the cylinder 18. The exterior body portion of the cylinder 18 at the threaded end of the cylinder is designated 30 and may serve to mount one of the struts such as the strut 11. Alternatively, the strut 11 could be secured to the piston 27 and the basket to the cylinder.

With the foregoing arrangement, it will be evident that swinging movement of the basket relative to the strut will cause the piston rod to rotate within the cylinder and because of the threads 28 and internal mating threads 29, an axial movement will be imparted to the piston rod and piston body 20 so that the body 20 moves axially within the cylindrical chamber 19.

In order to avoid back lash in the mating screw or gear teeth 28 and 29, a tapered bolt 31 is received in a counterbore formed in the end of the piston rod 26 and the threaded end of the rod is slotted such as indicated at 32 so that some of the threads are segmented. The bolt 31 itself may be threaded internally of the piston rod 26 as at 33. Because of the taper on the bolt, threading in of the bolt will radially expand the segmented threads to thus urge them against the internal threads and prevent back lash.

The assembly is completed by the provision of a fluid passage means 34 shown in the upper portion of the main cylinder 18. This fluid passage means provides communication between a portion of the cylindrical chamber 19 on one side of the piston body 20 and the other side of the piston body. A fluid passage restricting means in turn may take the form of a needle valve 35 with suitable threads 36 for adjusting the degree of restriction. It will be seen that axial movement of the piston body 20 within the cylindrical chamber 19 will urge fluid through the fluid passage means 34 and the resistance to this fluid flow may be adjusted by the needle valve.

FIG. 4 illustrates in perspective view the segmented end portion of the piston rod 26 preparatory to receiving the taper bolt 31. As shown in FIG. 4, the segmenting of the threads is accomplished preferably by providing four lateral slots spaced at 90 so that in addition to the slot 32 there are provided slots 37, 38 and 39. The tapered wall of the bolt 31 is shown at 40 and it will be evident that as the bolt is threaded into the counterbore in the end of the piston rod, this wall will cam radially outwardly the segmented thread portions to prevent the back lash as described heretofore.

The overall physical dimensioning of the rotary dampener as described in FIG. 3 is important. In the preferred embodiment, the diameter of the cylindrical chamber is at least four times the axial length of travel of the piston body 20 between the reduced diameter end openings 22 and 23. Thus, a relatively large surface area is provided on each side of the piston body against which axial movement of the body is resisted by suitable hydraulic fluid F in the cylindrical chamber. In other words, because of the large surface area of the piston body, a resistive force to rotation of the piston rod can be made appreciable notwithstanding the mechanical advantage normally realized in a conversion of rotary motion to axial motion by means of engaged threads.

The pitch of the threads 28 and cooperating internal threads 29 is such that complete axial travel of the piston body from one end of the cylindrical chamber to the other is effected for a relative rotation between the piston and cylinder of less than 360. If the pitch is shallow, the axial length of the interior cylindrical chamber 19 can be relatively short. On the other hand, the pitch of the threads should be sufiiciently steep that a proper balancing between the hydraulic force acting against movement of the piston body and the mechanical advantage realized through the conversion of rotary to axial motion is such that the rotary motion will be damped as desired. Finer dampening adjustments and force adjustments can be achieved by adjustment of the needle valve 35.

OPERATION The operation of the hydraulic rotary dampener will be evident from the foregoing description. When the dampener is used to critically damp swinging movements of a basket such as described in FIG. 2, the piston rod is secured to the basket and the cylinder secured to one of the struts, the axis of swinging movement being coaxial with the cylinder and piston rod as described heretofore. With particular reference to FIG. 3, if the basket 10 swings, the threaded engagement of the piston and cylinder will result in axial movement of the piston body 20 in the chamber 19 thereby forcing fluid past the needle valve and passage means 34 to the other side of the piston body. Swinging in an opposite direction it will result in a reverse flow of fluid. It will be evident that the resistance to such movement can readily be adjusted by the needle valve.

Should the threaded connection between the piston and cylinder become worn, it is only necessary to tighten the tapered bolt 31 to expand the threaded structure of the piston rod against the internal threads. Thus wear as well as back lash can readily be compensated for by the structure described.

The slight axial movement of the basket relative to the strut is accommodated by sliding of a journal shaft in the journal 17 for the other strut 12. With this arrangement, the slight lateral movement of the basket 10 can take place without introducing any strain or change in distance between the struts 11 and 12.

It should be understood, as stated that the connections of the strut and basket can be reversed. Further, while complete axial movement preferably takes place for less than 360 relative rotations such is not essential to the invention.

While the invention has been described in combination with a basket and boom structure, it will be evident that the hydraulic rotary dampener will have many applications aside from its preferred use.

What is claimed is:

l. A hydraulic rotary dampener comprising: a cylinder; a piston means in said cylinder, a portion of said piston means having threads mating with internal threads in said cylinder so that relative rotation between said piston means and cylinder results in axial movement of said piston means in said cylinder; hydraulic fluid in said cylinder; restricting passage means through which fluid can flow from one side of said piston means to the other upon axial movement of said piston means in said cylinder whereby relative rotary motion between said piston means and cylinder is dampened by said fluid.

2. The subject matter of claim 1, in which said piston means includes a piston body; a piston rod mounting said body intermediate its ends, said cylinder having reduced diameter end openings receiving the ends of said piston rod, the diameter of said piston body being at least four times the axial distance of movement of said piston body between said reduced diameter end openings so that a relatively large surface area on either side of said piston body is provided against which said axial movement is resisted by said fluid.

3. The subject matter of claim 2, in which the pitch of said threads mating with internal threads in said cylinder is such that the maximum axial movement of which said piston body is capable in said cylinder results with a relative rotation between said piston means and cylinder of less than 360.

4. A hydraulic rotary dampener for dampening swinging movement of a first member relative to a second member, comprising, in combination:

a. a cylinder having a central cylindrical chamber, a

reduced diameter first end opening and a reduced diameter second end opening, said second end opening having internal screw threads;

b. a piston body in said cylindrical chamber with its periphery in sealing relationship with the interior cylindrical wall of said cylindrical chamber;

0. a reduced diameter piston rod mounting said piston body intermediate its ends, said ends being positioned respectively in the first and second end openings of said cylinder, the end portion of said piston rod in said second end opening having external screw threads mating with said internal screw threads whereby relative rotation of said piston rod and cylinder causes said piston body to move axially in said cylindrical chamber;

. hydraulic fluid in said cylindrical chamber;

e. fluid passage means placing the portion of said cylindrical chamber on one side of said piston body in communication with the portion of said cylindrical chamber on the other side of said piston body so that axial movement of said piston body forces fluid to move through said fluid passage means from one side of the piston body to the other; and

f. fluid passage restricting means for varying the resistance of said fluid passage means to fluid flow therethrough whereby when said first member is secured to said piston rod and said second member secured to said cylinder such that relative swinging movement between said first member and second member about an axis coaxial with said cylinder and piston rod takes place, said swinging movement is dampened by said hydraulic dampener.

5. The subject matter of claim 4, in which the end of said piston rod having external threads is counterbored and laterally slotted so that some of said external threads are segmented; and a tapered bolt threadly receivable in said counterbore such that inward threading of said bolt causes its tapered surface to radially expand the segmented external threads against said internal threads to thereby eliminate back lash in said threads.

6. The subject matter of claim 4, in which said fluid passage means is in said cylinder and said fluid passage restricting means comprises a needle valve for adjusting the resistance to fluid flow through said passage.

7. The subject matter of claim 4, including said first and second members in combination with said rotary dampener, one of said members comprising a basket structure for supporting a man on the end of a boom and the other of said members comprising a strut on the end of said boom, so that swinging movement of said basket relative to said strut is dampened.

8, The subject matter of claim 7, including O-ring seals about the ends of said piston rod for providing a seal with the reduced diameter end openings; and a larger diameter O-ring about the periphery of said piston body for providing a seal with the interior wall of said cylindrical chamber.

9. The subject matter of claim 4, in which the diameter of said cylindrical chamber is at least four times the axial length of travel of said piston body in said cylindrical chamber between the reduced diameter end openings to provide a relatively large surface area on either side of said piston body against which axial movement is resisted by said fluid.

10. The subject matter of claim 9, in which the pitch of said external threads on the end of said piston rod is such that complete axial travel of said piston body from one end of said cylindrical chamber to the other is effected for a relative rotation between the first and second members of less than 360. 

1. A hydraulic rotary dampener comprising: a cylinder; a piston means in said cylinder, a portion of said piston means having threads mating with internal threads in said cylinder so that relative rotation between said piston means and cylinder results in axial movement of said piston means in said cylinder; hydraulic fluid in said cylinder; restricting passage means through which fluid can flow from one side of said piston means to the other upon axial movement of said piston means in said cylinder whereby relative rotary motion between said piston means and cylinder iS dampened by said fluid.
 2. The subject matter of claim 1, in which said piston means includes a piston body; a piston rod mounting said body intermediate its ends, said cylinder having reduced diameter end openings receiving the ends of said piston rod, the diameter of said piston body being at least four times the axial distance of movement of said piston body between said reduced diameter end openings so that a relatively large surface area on either side of said piston body is provided against which said axial movement is resisted by said fluid.
 3. The subject matter of claim 2, in which the pitch of said threads mating with internal threads in said cylinder is such that the maximum axial movement of which said piston body is capable in said cylinder results with a relative rotation between said piston means and cylinder of less than 360*.
 4. A hydraulic rotary dampener for dampening swinging movement of a first member relative to a second member, comprising, in combination: a. a cylinder having a central cylindrical chamber, a reduced diameter first end opening and a reduced diameter second end opening, said second end opening having internal screw threads; b. a piston body in said cylindrical chamber with its periphery in sealing relationship with the interior cylindrical wall of said cylindrical chamber; c. a reduced diameter piston rod mounting said piston body intermediate its ends, said ends being positioned respectively in the first and second end openings of said cylinder, the end portion of said piston rod in said second end opening having external screw threads mating with said internal screw threads whereby relative rotation of said piston rod and cylinder causes said piston body to move axially in said cylindrical chamber; d. hydraulic fluid in said cylindrical chamber; e. fluid passage means placing the portion of said cylindrical chamber on one side of said piston body in communication with the portion of said cylindrical chamber on the other side of said piston body so that axial movement of said piston body forces fluid to move through said fluid passage means from one side of the piston body to the other; and f. fluid passage restricting means for varying the resistance of said fluid passage means to fluid flow therethrough whereby when said first member is secured to said piston rod and said second member secured to said cylinder such that relative swinging movement between said first member and second member about an axis coaxial with said cylinder and piston rod takes place, said swinging movement is dampened by said hydraulic dampener.
 5. The subject matter of claim 4, in which the end of said piston rod having external threads is counterbored and laterally slotted so that some of said external threads are segmented; and a tapered bolt threadly receivable in said counterbore such that inward threading of said bolt causes its tapered surface to radially expand the segmented external threads against said internal threads to thereby eliminate back lash in said threads.
 6. The subject matter of claim 4, in which said fluid passage means is in said cylinder and said fluid passage restricting means comprises a needle valve for adjusting the resistance to fluid flow through said passage.
 7. The subject matter of claim 4, including said first and second members in combination with said rotary dampener, one of said members comprising a basket structure for supporting a man on the end of a boom and the other of said members comprising a strut on the end of said boom, so that swinging movement of said basket relative to said strut is dampened.
 8. The subject matter of claim 7, including O-ring seals about the ends of said piston rod for providing a seal with the reduced diameter end openings; and a larger diameter O-ring about the periphery of said piston body for providing a seal with the interior wall of said cylindrical chamber.
 9. The subject matter of claim 4, in which the diameTer of said cylindrical chamber is at least four times the axial length of travel of said piston body in said cylindrical chamber between the reduced diameter end openings to provide a relatively large surface area on either side of said piston body against which axial movement is resisted by said fluid.
 10. The subject matter of claim 9, in which the pitch of said external threads on the end of said piston rod is such that complete axial travel of said piston body from one end of said cylindrical chamber to the other is effected for a relative rotation between the first and second members of less than 360*. 